1. Field of the Invention
The present invention relates to a technology of estimating a fuel temperature of each part (for example, an injection nozzle, a pressure accumulator, a high-pressure pump) of a fuel channel in a vehicle such as an automobile.
2. Description of Related Art
A fuel injected from a fuel injection device into a cylinder becomes different in temperature immediately before the injection according to an engine and a circumstance state (temperature condition) thereof until the fuel is injected from the fuel injection device. Then, a density of the fuel becomes different due to a difference in the fuel temperature immediately before the injection.
Therefore, in a case in which the fuel is supplied to the engine by the fuel injection device, there is a need to correct an injection pressure or a combustion pressure in consideration of a change of the fuel density caused by the difference in the fuel temperature or an influence of an injection pressure, and the fuel temperature is necessarily monitored with accuracy in order to achieve a desirable combustion state.
The fuel temperature has been measured using a thermometer (temperature sensor) in the related art, but in a case in which the temperature sensor malfunctions for some reason, the desirable combustion state may be not secured. In addition, if the fuel temperature can be accurately monitored without the use of the temperature sensor, the number of components can be reduced, and the cost can be reduced.
Therefore, there is a demand for calculating the fuel temperature in an automobile provided with a common rail fuel injection device without the use of the thermometer (temperature sensor) in the related art.
In order to meet such a demand, there is already disclosed a technology of calculating the fuel temperature in the automobile provided with the common rail fuel injection device without the use of the thermometer (for example, see Patent Document 1). According to the related art (Patent Document 1), the fuel temperature is estimated based on a water temperature of the engine and a characteristic of the fuel temperature, and the estimation value of the fuel temperature is corrected using the fuel remainder in a fuel tank.
In this regard, there is a demand for measuring the fuel temperature with a higher accuracy compared to the related art disclosed in Japanese Patent Application Laid-open Publication No. 2005-76596. However, there is proposed no technology that can meet such a demand at the present time.